Long path tracer render - stuck on uninitialized/long sample times

Wondering if anyone can help. Trying to do a still render that has a moving car, camera and wheels to create motion blur.
I’m using path tracer and for some reason it’s taking forever to render. It either gets stuck on uninitialized or samples are taking forever to go through.
Don’t normally have any issues rendering with path tracer and have rendered plenty of stuff in the past in the same way.
Not rendering anything super high res either but have tried using high resolution in MVQ but not had any luck.
Sorry it’s not the best description but really stuck on what could be the issue for it not rendering.
Thanks!